Patients suffering from certain body injuries typically experience either an increase or decrease in body temperature as a result of the injury. For example, certain patients experience hyperthermia or fever following significant brain injury or major cardiovascular surgery. In another example, certain patients experience spontaneous hypothermia following cardiac arrest, brain trauma, or extensive bleeding. In both examples, the presence of a hypothermic or hypothermic state is prognostic of a poor neurological outcome or mortality of the patients and the patients typically require body temperature management to reverse the hyperthermic or hypothermic states. For example, in the case of a patient experiencing a hyperthermic state, healthcare professionals typically minimize or prevent fever in the patient using analgesic therapy and body surface cooling to reduce the patient's body temperature, improve neurological outcomes, and improve the likelihood of the patient's survival. In the case of a patient experiencing a hypothermic state, healthcare professionals typically increase the body temperature of the patient using body surface warming devices, such as heating blankets, to improve the likelihood of the patient's survival.
While heath care professionals utilize body temperature management to reverse the hyperthermic or hypothermic state of a patient, healthcare professionals also utilize body temperature management techniques to induce hypothermia in certain case. For example, the therapeutic use of mild to moderate hypothermia (temperature 2 to 5 degrees centigrade below normal) has been shown to reduce the secondary loss of vital organ tissue following an ischemic event such as stroke or cardiac arrest (e.g., heart attack), and following trauma. Therapeutic hypothermia also effectively reduces inflammation and edema in tissue following injury.
Historically, health care professionals have induced systemic hypothermia (e.g., whole body cooling) in a patient by immersing the patient's body in a cool bath. Currently, there are several conventional systemic hypothermia systems available. Such conventional systems include blankets or pads where cooled water is circulated through channels in the walls of the blanket or pad. As the patient's body contacts the walls of the blanket, the cooled water within the channels carries heat away from the patient's body, thereby inducing systemic hypothermia in the patient.
Health care professionals also use devices that provide vascular cooling to a patient to reduce the patient's body temperature. Such devices provide either in vivo and ex vivo cooling of blood, relative to the patient.
For example, a typical in vivo vascular cooling catheter, such as available from Radiant Medical Corporation, Alsius Medical, or InnerCool Medical, has a distal end placed within a vena cava of a patient and a proximal end coupled to refrigeration-based cooling console located in the vicinity of the patient (e.g., bedside). During operation, the console pumps cold saline through the catheter (e.g., from the console, to the distal end of the catheter, and back to the console). As blood flows through the vena cava, the blood contacts the distal end of the cooling catheter. The distal end of the cooling catheter acts as an in vivo heat exchanger, absorbing heat from the blood as the blood flows past the distal end of the catheter, while the cold saline within the catheter carries heat away from the blood, thereby cooling the blood and reducing the body temperature of the patient.
In another example, healthcare professionals typically utilize an ex vivo vascular cooling device during cardiovascular surgery. The use of hypothermia during cardiac surgery aids in protecting cardiac and cerebral tissues during periods of reduced blood circulation during the surgery. During cardiovascular surgery healthcare professionals perform a hypothermic bypass technique where blood is pumped from a patient, through a bedside machine that cools and oxygenates the blood, and back into the patient. The reduced temperature blood induces hypothermia within the patient